[Devel] Re: FreeType -> PS/PDF

[Leonard Rosenthol]

At 05:22 PM 12/23/2001 +0000, Vadim Plessky wrote:
> "Providing a way to convert the used fonts to PostScript fonts" is indeed a
> quite important issue.

        I wrote for my former employer the code for using FreeType to get 
the information necessary to embed fonts in PDF files.  I've been meaning 
to rewrite it and add it to the FreeType distro.

        Some of that work could also be used for PS generators, but there 
are difference in certain types of font handling (most notably that PS 
wants TTF fonts as Type42, while PDF can handle them natively).

        I do think, however, that such a module for FT would be a valuable 
one and I'm certainly willing to help work on it!


> Font conversion (TrueType -> PostScript) is happening in Qt library.
>
> Latest release of Qt, Qt3, allows either Font Embedding (via font conversion
> of TTF fonts or "direct embedding" of PS T1 fonts) or generating PS/PDf "as
> is", without any fonts embedded (it's configurable).

        Do you know what they are doing in Qt?  Is it full or subset 
embedding?  Is it Type 42, conversion of TTF->Type 1, or do they do "fake 
subsetting" by conversion Type 3's?


> Another quite important question is support for SVG.
> You have mentioned that:
> " It would be capable of generating outlines. Converting them to
> PostScript is trivial."
> Does it mean that converting outlines to SVG would also be trivial?

        Hopefully, like Postscript, it would mean treating text as text 
(and NOT converting to outlines!) with optional CEF font embedding.


> PDF is definitly getting higher
> priority in Adobe than PostScript, so I would say generating PDF, but not
> PostScript, from vector objects should be top prioroty for all projects
> related to layouting.

        I agree!!!!

        Especially since it provides a way for inclusion of non-layout 
information (hyperlinks, bookmarks, structure, etc.) that isn't present in 
Postscript and can be useful for electronic documents.   And if you want 
Postscript, then use pdf2ps (or the equivalent) to convert.


> There are several very important issues come here to mind.
>  a) font hinting
>  b) anti-aliasing

        I'll second Vadim on this one also!  These are the two main reason 
why you do NOT convert text to outlines (ever!) unless you plan to "play 
with the letter shapes".  Hints and anti-aliased rendering are VERY 
IMPORTANT for both printed as well as screen rendered text.

        The other item that is missing from this list, when considering 
the possibility that the data will go to a format for distribution to other 
people (eg. SVG, PDF) is that without text you can't do textual 
analysis!   This means that the document can't be searched or indexed - AND 
it also means that it is no longer accessible to people who require screen 
readers.


> I have checked and found that Adobe uses [in their Adobe SVG 3.0
>  plugin] own cross-platform graphics library. Most likely, it's used not only
>  in SVG plugin but in Adobe Illustrator, Pagemaker, and other programs which
>  require either PostScriupt or SVG rendering.

        Adobe has two core libraries that provide the graphics services to 
their applications.  CoolType is the name of their text & font library, and 
AGM (Adobe Graphics Manager) is the 2D graphics/vector stuff.  You can see 
these if you are running on Mac OS or Windows with any Adobe application - 
look in the DLL's/shlibs at the names.


> |   - the TrueType fonts can be either converted to Type42 with the
> |   algorithm taken from ttf2type42 or converted to Type1 with the
> |   algorithm taken from ttf2pt1

        Be careful with this!  Those utilities are very nice for simple 
things, but they do not deal with issues such as conversion of hinting 
data, that as noted above, is quite important for material destined for 
distribution instead of printing.


> |   - the other fonts can be rasterized to bitmaps and then converted
> |   to the Type1 fonts with the algorithm taken from ttf2pt1

        If you are going to rasterize to bitmap (yuch!), then you should 
at least convert to Type3, which is designed for this type of data.  That's 
why dvips has for years been creating documents that look like crap on 
screen but print nicely.


Leonard